Research On Algicidal Effect And Mechanism Of Algicidal Bacteria L7 On Microcystis Aeruginosa

With the increasingly serious eutrophication and frequent outbreaks of algal bloom, it is imperative to explore effective methods to prevent algal bloom. The use of algicidal bacteria is considered as a new method of controlling algae has become the hotspot of biological control of algae.One algicidal bacteria, strain L7, was isolated from a eutrophic pond in the town of Guangzhou, which belongs to Bacillus cereus. Based on the existing research, the author studied the algicidal effect of L7 on Microcystis aeruginosa, and explored its algicidal mechanism. The main results were as follows:1. The algicidal effect of L7 on Microcystis aeruginosaThe algicidal effect of L7 on Microcystis aeruginosa was consistents with the relationship of "concentration-effect", showing"low concentration promoted, high concentration inhibited". During 7d's consecutive experiment, the algicidal effect under different temperature conditions were 25℃>35℃>15℃. The algicidal effect in the 12h: 12h light and dark cycle was stronger than in illumination and in darkness; At different pH level, the algicidal effect were pH 9.0>pH 7.0>pH 6.0>pH 8.0>pH 10.0.2. The effect of L7 on the physiological characteristics of Microcystis aeruginosaUnder the treatment of high concentration L7 (ρL7>107cfu/mL), the dehydrogenase activity, soluble protein content, soluble carbohydrate content of Microcystis aeruginosa decreased. The chlorophyll, carotenoids and phycocyanin of Microcystis aeruginosa decreased significantly. The MDA content increased. We conclude that the algicidal mechanism of L7 on Microcystis aeruginosa was: L7 inhibited the photosynthesis system activity of Microcystis aeruginosa, which led to reducing the photosynthesis, and then reducing the dehydrogenase activity, soluble protein, soluble carbohydrate content, making bilchenical reations slow down, ultimately affecting the cell division of algae.3. The effect of L7 on the cell biological characteristics of Microcystis aeruginosaThe biological characteristics of the algae in the algicidal cycle by FCM analysis showed that the algicidal trends were in steps. Firstly, the Microcystis aeruginosa cell membrane was destroyed, then the chlorophyll was damaged, resulting in the non-natural death of the algae cells at the last step. In the continued effect of L7, the nucleic acids of the algae cells was also damaged severely. 4. The transfer of phosphorus during the algicidal processAlthough L7 suppressed the proliferation of the algae cells, the absorption of phosphorus in water was not subject to its suppression, and the phosphorus could be accumulated in the algae in the latter stages.5. The feedback and induction of intact algal solution to L7Adding intact algal solution of Microcystis aeruginosa into the culture process of L7 would help improve the aligicidal effect of algicidal components to Microcystis aeruginosa, but there was no significant difference among different growth cycles of algae; With the addition of the intact algal solution of Microcystis aeruginosa increased, the algicidal effect of the algicidal components to Microcystis aeruginosa increased, showing the relationship of"dose-effect".